Communism and Fascism have both played a very decisive role in the 20th century. They had a big impact on all the major geopolitical issues of this century; the Russians Revolution of October 1917, the Spanish civil war, WWII, Cold War, Vietnamese's wars, Cuba's regime etc. It is commonly agreed that the regimes and governments led by both of these ideologies were not very respectful of basic rights such as freedom and equality, and sometimes much worse, were the instigators of crimes and massacres. We are now going to leave the very rational democratic way of thinking, to try to go into this complex event that occurred under the name of fascism and communism, in order to try to analyze which one of these two ideologies caused the worst massacres and disasters. In order to respond accurately, it is strongly recommended to define exactly the basis of communist and fascist ideologies, and to then try to analyze the different way of expressions of these ideologies, and eventually the consequences.